\documentclass{standalone}
\usepackage{tikz}
\usepackage{ctex,siunitx}
\setCJKmainfont{Noto Serif CJK SC}
\usepackage{tkz-euclide}
\usepackage{amsmath}
\usepackage{wasysym}
\usetikzlibrary{patterns, calc}
\usetikzlibrary {decorations.pathmorphing, decorations.pathreplacing, decorations.shapes,}
\begin{document}
\small
\begin{tikzpicture}[>=latex,xscale=0.6]
  % \useasboundingbox(0.9,0)rectangle(5.1,5);
  \draw [->](-.5,0)--(8.5,0)node[right]{$t$(s)};
  \draw [->](0,-1.5)--(0,2.5)node[right]{$i$(A)};
  \draw [ultra thick] plot[domain=0:3.14*2.5, samples=1000] function{cos(x)};
  \draw [dashed](0,1)--(2*3.1416,1);
  \draw [dashed](0,-1)--(3.1416,-1);
  \node at (0,1) [left]{$+10$};
  \node at (0,-1) [left]{$-10$};
  \foreach \x in {0.05,0.1,0.15,0.2,0.25}
  {
      \node at (\x*31.416, 0)[below]{$\x$};
      \draw(\x*31.416, 0)--(\x*31.416, .1);
  }
  \node at (-.25,-.25){$0$};
\end{tikzpicture}
\end{document}